It is known in the art relating to engine cooling systems utilizing centrifugal coolant pumps to provide positive pressure at the inlet of a pump to extend the speed and temperature conditions under which the pump may be operated without cavitation occurring at the pump inlet, in other words, to suppress cavitation. Positive inlet pressure may be provided by a head of water or coolant obtained, for example, by mounting a coolant tank at a desired height above the pump inlet, so that the weight of the column of water provides a pressure head. Alternatively, the cooling system may be pressurized.
In a known application for railway locomotives having a relatively low coolant tank mounting, the coolant system has been pressurized in operation by the addition of a water inlet tee shown in FIG. 6 and formed similar to a jet pump or aspirator but functioning to increase the pump inlet pressure. The prior inlet tee utilized a straight sided nozzle for projecting a jet of water, or coolant, into a chamber to which the coolant tank was connected and which discharged into a diverging diffuser connected to the pump inlet. The pressure head supplied by the tank was thereby supplemented at the diffuser inlet by conversion of some of the dynamic head of the water jet into increased inlet pressure at the pump inlet.
Operation of the inlet tee was satisfactory, however, it was formed as a single casting, which, for differing applications, required provision of expensive casting dies. An improved design was desired which would reduce complexity and modification costs while providing equivalent or improved performance in engine applications.